TaromA380 From Romania, joined Sep 2005, 334 posts, RR: 0 Posted (8 years 11 months 3 weeks 2 days 23 hours ago) and read 4106 times:
When big airliners are landing, the gear wheels are immobile, thus the tires will get significant stress when touching the runway at ~150 knots, with such a mass pressure upon them. Everyone knows the dark rubber smoke which appears on each landing. The result is that the tires will need to be replaced after a few (or more) dozen landings.
Now, I ask you : why not putting a small electrical motor on the gear, to accelerate the wheels near the landing speed just before touching down, avoiding the abrasive contact shock thereby the degradation of the tires ?
I think it would be economically wise on long term. Just think about how many times an airliner needs to change the tires because of repeated landing shocks that reduce their size until the security limit. Moreover, tires would be much economical to acquire, not needing to be specially reinforced to support dozens highly abrasive landings.
I bet you'll come with the "weight" motive, but I think those electrical motors doesn't need to be big, the accelerating of the wheels would be in the air, without friction, so no need to huge power. How heavy two main devices plus one smaller device for the nose wheel would be ? 100 kg overall ? What is 100 kg besides the 560.000 kg of the A380 ? Not even talking about the tires weight save.
And remember, a big airliner like the A380 needs not less than 22 tires replacement !!
TedTAce From , joined Dec 1969, posts, RR:
Reply 2, posted (8 years 11 months 3 weeks 2 days 23 hours ago) and read 4088 times:
I think it comes down to weight/complexity/cost issue. I'm POSITIVE that tire wear, when compared to additional fuel burn and complexity/cost of such a system, makes burning rubber a more appealing option.
ZSOFN From United Kingdom, joined Jun 2005, 1413 posts, RR: 6
Reply 5, posted (8 years 11 months 3 weeks 2 days 18 hours ago) and read 3966 times:
The main reason is actually due to the large gyroscopic effect the spinning tyres would have, making the aircraft very difficult to manouvre on final approach. I found this out from an SAA technician in JNB.
FredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 6, posted (8 years 11 months 3 weeks 2 days 18 hours ago) and read 3955 times:
Yes, especially significant compared to the low mass and low RPM of other rotating objects on the aircraft... such as the engine fans. Hangar tale, that one. The aircraft aren't hard to manouever after taking off, are they? Even before the gear is retracted/the wheels braked.
Most tire wear is during taxi anyway. There's just not much wear to be saved. Read the previous thread, you are reiterating things which were said there.
I thought I was doing good trying to avoid those airport hotels... and look at me now.
GRZ-AIR From Austria, joined Apr 2001, 574 posts, RR: 4
Reply 8, posted (8 years 11 months 3 weeks 9 hours ago) and read 3678 times:
Tire wear is good for economy... there are many ways how tires could be improved to withstand more ldgs and t/o's..but then fewer would be needed which is of no interest to the tire manufacturers.
The best solution I came accross once was a tire which had a little "hump" going around the outside of the tire...thus building up friction agains the air which resulted in accelerating the tire up to landing speed...tests showed that the lifetime of these tires were much higher than the ones used today..
The idea was however (for obvious above stated reasons) turned down by the large aircraft tire corporations..
Good idea though! And far better than any "electrical" motor and other crap..